You should have known a 380mm rotor would not be an easy fit in an 18" wheel; actually it's pretty much needs a 19" wheel.
The StopTech kit for the E9x M3 is also a 380mm kit, so it won't help you either.
Let me get this straight... You are swapping out parts designed by some of the top engineers in the world because some guys sponsored by a company told you it's "better??" But when you ask the same guy about tracking, "oh no, I have a kid now" or "I just detailed my car." or "i just got new tires."